物理化学学报 >> 2007, Vol. 23 >> Issue (07): 1013-1017.doi: 10.1016/S1872-1508(07)60056-4

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Mn(II)和Ce(IV)离子对铬酸氧化乳酸的影响

MALIK Maqsood Ahmad; KHAN Zaheer   

  1. Department of Chemistry, Jamia Millia Islamia (Central University), New Delhi 110025, India
  • 收稿日期:2007-03-13 修回日期:2007-04-09 发布日期:2007-07-03
  • 通讯作者: KHAN Zaheer E-mail:drkhanchem@yahoo.co.in

Effect ofMn(II) and Ce(IV) Ions on the Oxidation of Lactic Acid by Chromic Acid

MALIK Maqsood Ahmad; KHAN Zaheer   

  1. Department of Chemistry, Jamia Millia Islamia (Central University), New Delhi 110025, India
  • Received:2007-03-13 Revised:2007-04-09 Published:2007-07-03
  • Contact: KHAN Zaheer E-mail:drkhanchem@yahoo.co.in

摘要: The kinetics and mechanismof lactic acid oxidation in the presence of Mn(II) and Ce(IV) ions by chromic acid were studied spectrophotometrically. The oxidation of lactic acid by Cr(VI) was found to proceed in two measurable steps, both of which gave pyruvic acid as the primary product in the absence of Mn(II).
2Cr(VI)+2CH3CHOHCOOH→2CH3COCOOH+Cr(V)+Cr(III)
Cr(V)+CH3CHOHCOOH→Cr(III)+CH3COCOOH
The observed kinetics was explained due to the catalytic and inhibitory effects of Mn(II) and Ce(IV) on the lactic acid oxidation by Cr(VI). The reactivity of lactic acid depends upon the experimental conditions. It acts as a two-or three-equivalent reducing agent in the absence or presence of Mn(II). It was examined that Cr(III) products resulting from the direct reduction of Cr(VI) by three-equivalent reducing agents. The oxidation of lactic acid follows the complex order kinetics with respect to [lactic acid]. The activation parameters Ea, △H#, and △S# were calculated and discussed.

关键词: Kinetics, Lactic acid, Cr(VI), Ce(IV), Mn(II), Oxidation

Abstract: The kinetics and mechanismof lactic acid oxidation in the presence of Mn(II) and Ce(IV) ions by chromic acid were studied spectrophotometrically. The oxidation of lactic acid by Cr(VI) was found to proceed in two measurable steps, both of which gave pyruvic acid as the primary product in the absence of Mn(II).
2Cr(VI)+2CH3CHOHCOOH→2CH3COCOOH+Cr(V)+Cr(III)
Cr(V)+CH3CHOHCOOH→Cr(III)+CH3COCOOH
The observed kinetics was explained due to the catalytic and inhibitory effects of Mn(II) and Ce(IV) on the lactic acid oxidation by Cr(VI). The reactivity of lactic acid depends upon the experimental conditions. It acts as a two-or three-equivalent reducing agent in the absence or presence of Mn(II). It was examined that Cr(III) products resulting from the direct reduction of Cr(VI) by three-equivalent reducing agents. The oxidation of lactic acid follows the complex order kinetics with respect to [lactic acid]. The activation parameters Ea, △H#, and △S# were calculated and discussed.

Key words: Kinetics, Lactic acid, Cr(VI), Ce(IV), Mn(II), Oxidation